1. Field of the Invention
The present invention relates to a novel process for the preparation of derivatives of maltooligosaccharides. More particularly, the present invention relates to a process for the preparation of derivatives of maltooligosaccharides having a high purity at a high yield.
The derivatives of maltooligosaccharides have been widely used as a substrate for determining .alpha.-amylase activity in human serum and urine, various physiologically active substances, natural dieteic sweetenings, coloring agents and the like. For example, when the derivatives of maltooligosaccharides are used as a substrate for the determination of .alpha.-amylase activity of the humor, there are advantages that such determination can be easily and simply carried out, and that said derivatives have a good adaptability to the analysis made using automatic analytical instruments.
2. Description of Related Art
Hitherto, a chemical synthetic process and an enzyme process have been known and used in the production of derivatives of maltooligosaccharides such as .alpha.,.beta.-phenylmaltooligosaccharides and the like.
A chemical synthetic process can be carried out as follows (see, Japanese Unexamined Patent Publication (Kokai) No. 54-25893): First, maltooligosaccharides such as maltopentaose or maltohexaose are acetylated to protect hydroxyl groups thereof. The acetylated maltooligosaccharides are then halogenated to introduce halogens into the reducing-end of maltooligosaccharides. Thereafter, the resultant halogenated acetylated maltooligosaccharides are reacted with substituted phenols in the presence of solvents such as pyridine and the like to obtain acetylated product of .alpha.,.beta.-substituted phenylmaltooligosides. The acetylated product is subjected to deacetylation to obtain a desired .alpha. or .beta.-substituted phenylmaltooligoside.
An enzyme process can be made as follows (see, Carbohydrate Research 61 (1978), 359-368): Alpha(.alpha.)-cyclodextrin and .alpha.,.beta.-phenylglucosides are reacted with transferases such as cyclodextrin glucosyltransferase or the like to produce a mixture of .alpha.,.beta.-phenylmaltooligosides. The resulting mixture is the fractionated by means of a column chromatography to obtain a desired .alpha. or .beta.-phenylmaltooligoside, for example, 4-nitrophenyl-.alpha.-D-maltoheptaoside.
Among these processes, the chemical synthetic process has, however, drawbacks such that the steps necessary to complete the process are numerous and troublesome, that the yield is low, and that .alpha.- or .beta.-linked derivatives can not be freely produced.
Also, while the enzyme process can be easily carried out due to simpleness of the reaction steps thereof, it has a tendency to produce a large amount of homologues which have a molecular weight close to that of the desired product. Thus, an actual product comprises a mixture of various oligosides having different degrees of polymerization of glucose. Therefore, to obtain a highly purified product, it was necessary to further carry out fractionation by using a chromatography. Moreover, this enzyme process had a drawback that a yield of the product is low.
In addition, as described in the above paragraph, derivatives of maltooligosaccharides having a high purity are required, when such derivatives are used as a substrate for the determination of activity of .alpha.-amylase in a humor. However, the above-described prior art processes are not satisfactory for this requirement, because using these processes, it is very difficult to produce highly purified derivatives of maltooligosaccharides.